I get asked all the time, "what type of wire do you use to build the cables?".  Some guys want marine grade wire or they heard that welding cable is the hot set up.  Below is a description of what we use and my opinions about if you should use be using marine grade wire on your Dodge Dart.

SGT Battery Cable:

We generally use SAE (Society of Automotive Engineers) SGT battery cable.  SGT designates the type of wire.  For example THHN is probably what you have wiring your house.  SGT is self extinguishing PVC insulation rated at 50 Volts.  It's typically rated for 85 or 105 degrees C.  This is the lowest cost wire of the 3 wire types discussed here and it does the job just fine.  The strands are larger than the other two, making the wire stiffer so it stays where you put it but still flexible enough to bend around tight corners. 

Pros: Lowest cost, SAE rating. 
Cons: Lowest temp rating (as low as 85C, about 185F).

SGX Battery Cable:

Sometimes we use SGX battery cable.  SGX uses a XLP insulation which has a higher temperature rating.  The trade off is the insulation is thicker and stiffer.  Often it has a higher strand count to make it flexible to help offset the stiffer insulation.  It also costs more. If you need the higher temp rating, it might be a good solution. 

Pros: SAE rating.  Higher temp rating (125C).
Cons: Stiffer, might be harder to route. More expensive.

Marine Grade:

There are several types of "Marine" wire.  It's usually rated for a higher temperature and "wet" (think submersed) applications. it is also has a requirement that it be "self-extinguishing".  That is extremely important on a boat in the middle of nowhere. SGT-M is SGT battery cable rated for marine use and is only a little more expensive than SGT.  Some  marine grade wire is "tinned" (plated) to help reduce corrosion and has a high strand count like welding cable.  it can get very expensive (twice as much).

 There was a time, when I was grumpier, when asked for a marine cable for a car that I would answer "Are you going to be taking your Taurus out to sea??".  I thought it was a waste of time, money and energy.  I still do in most cases.  Then a friend pointed out that perhaps marine cable would help if one lived somewhere near the ocean and a salt atmosphere, or maybe salt on the roads.  Or perhaps the self-extinguishing characteristic was of critical importance to the customer.  I  guess that might be true.  I live in the desert so I don't have any personal experience with such things.  However, I can tell you that once we install the lugs, terminals and the heat shrink is applied, no copper is exposed so I honestly doubt it actually makes much difference in automotive applications.

Because of the high cost I only stock small quantities of marine cable but if I don't have it, I can order it.  Expect it to take a couple weeks longer. 

I absolutely believe that it must be used on boats. After all that's what it's made for.   I will not build a cable intended for marine use out of automotive wire.  Don't bother asking.

Pro's: High temp, Flexibility (sometimes), Corrosion resistance, Wet applications. Self-extinguishing. Con's: Expensive, Sometimes Hard to get out here in the middle of the Arizona desert. Consider it a Special Order,

Welding cable:

Welding cable is built to be flexible so the welder does not have to work hard to drag the wires around.  It usually has a high temp rating and a soft flexible insulation.  I have seen it swell up when exposed to oil.; do NOT use it in an application where it will get oily. For that reason I do not recommend it for automotive applications.  Welding cable tends to be large gauge wire so I think the guys that claim welding cable is the very best stuff to use do so because they are comparing very large 2/0 welding cable to a small #2 battery cable.  They don't really understand why it's better.  If they compared apples to apples, a 2/0 welding cable to a 2/0 battery cable in a oily under-hood application they would agree that the SGT/SGX battery cable is a better choice.  I do NOT I stock welding cable but  I can order it.  It does work great as booster cable where the ability to roll it up and put it behind the seat is important.

Pro's: High temp, Very flexible.
Con's: Expensive. Soft insulation.  Limited abrasion resistance. Not oil resistant.  Not SAE approved.

High Strand Count:

Some folks are looking for high strand count battery cable.  Perhaps they have heard it's somehow "better".  Some folks think that it carries more power due to "skin effect".  That is just plain false.  Skin effect is a high frequency phenomenon (think radio frequency or microwave) and is nonexistent at 12V DC.  The high strand count is more flexible but in an automotive application the cables get installed once then hopefully they never move again.  So flexibility isn't really a huge issue.

OFC (Oxygen Free Copper):

Don't waste your money. This stuff is just a clever way for stereo salesmen to get more of your hard earned money.  If you are seriously thinking of spending big bucks to buy OFC wire because some high school drop out salesman at the stereo shop told you it would make your stereo sound better, you really need to read our OFC (Oxygen Free Copper) page.

Summary:

For boats you got to have marine.  I'm no legal expert but isn't that a Coast Guard rule?  

Welding cable makes great booster cables or portable inverter cabling.  Nice and flexible for when you roll them up and put the back in the trunk.